The serial featured an adaptation of the Fawcett Comics superhero, placed within an original story in which he fights a mysterious masked criminal mastermind, called The Scorpion, who is determined to gain total control of a magical gold scorpion figurine. It is actually a disguised optical weapon of incredible power (including, but not limited to, melting rock via a projected death ray).

Billy Batson is an assistant radio operator with the Malcolm archaeological expedition to "the Valley of the Tombs" in Siam. The expedition is attacked by natives but Tal Chotali parleys with Rahman Bar. A sacred legend states no desecration will occur until the volcano, Scorpio, is active again. At the tombs, Billy refuses to enter the inner tomb as it would desecrate the religious beliefs of others. Instead he goes to pack pottery in another tunnel. In the inner tomb, Tal Chotali, Prof Malcolm, Prof Luthor Bentley, Dwight Fisher, and Dr Stephen Lang, find the Golden Scorpion. A ray from the Scorpion collapses the entrance to the tombs and opens a hidden passage between Billy and the ancient wizard Shazam. Shazam grants him the ability to change into Captain Marvel in order to prevent the Golden Scorpion from falling into the wrong hands. It is his "duty to see that the curse of the Scorpion is not visited on innocent people."

The lenses from the Golden Scorpion are divided among the five scientists. Scorpio then erupts which triggers a native attack. However, the masked mystery villain the Scorpion is orchestrating it, stealing one of the lenses during the hostilities. The expedition is rescued by cavalry from Fort Mooltan. Captain Marvel then flies to a group of natives with a machine gun, knocks them out by throwing one at the other, and takes over the gun. Marvel then throws aside the gun and attacks with his bare fists. Marvel learns he is invulnerable as bullets bounce off his chest.

The expedition then returns to the United States, where the Scorpion attempts to acquire all of the lenses and the Scorpion device for his own power. Several expedition members are killed in his quest despite Captain Marvel's continual efforts to thwart the villain. Billy Batson soon decides that the man behind the Scorpion's mask is one of the team.

Eventually a second expedition sets out because it has been learned that Long had actually hidden his lens in the tomb. The Scorpion witnesses Billy's change during this and captures him - tying him up and gagging him. The Scorpion interrogates Billy for the secret. When Billy agrees to tell him, The Scorpion removes the gag and Billy says "Shazam", which transforms him into Captain Marvel.

The Scorpion is then revealed to be Bentley. He is killed by the disillusioned native chief, Rahman Bar, who uses the Scorpion in death ray mode. Captain Marvel then tosses the scorpion statue into the molten lava to prevent mankind from using it for evil in the future. Once it is destroyed, Captain Marvel is transformed back into Billy Batson instantly as there is no need for a protector for the scorpion anymore.